124 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Pilematechinus. 



A. Agassiz, 1904. Mem. M. C. Z., 31, p. 165. 

 Type, Cystechinus rathbuni A. Agassiz, 1898. Bull. M. C. Z., 32, p. 79. 



This genus has been as exhaustively studied by Agassiz and by Alortensen 

 as the nature of the available material would permit, so there is nothing new to 

 be added. 



Key to the Species of Pilematechinus. 



Genital pores 4; lower margin of periproct some distance above ambitus rathbuni. 



Genital pores 3; lower margin of periproct just above ambitus vescica. 



Pilematechinus rathbuni. 



Cystechinus rathbuni A. Agassiz, 1898. Bull. M. C. Z., 32, p. 79. 

 Pilematechinus rathbuni A. Agassiz, 1904. Mem. M. C. Z., 31, p. 165. 



This is the Panamic species taken at 1672-1823 fms. by the Albatross. 

 Pilematechinus vescica. 



Cystechinus vescica A. Agassiz, 1879. Proc. Amer. Acad., 14, p. 209. 

 Pilematechinus vescica A. Agassiz, 1904. Mem. M. C. Z., 31, p. 232. 



This species was taken by the Challenger between Juan Fernandez and 

 Chile at the remarkable depth of 2225 fms., over 2.5 miles. 



ECHINOCORYTHIDAE Gregory. 



This family includes but a single Recent genus and species. I have had no 

 opportunity of examining a specimen, so simply follow de Meijere and Mortensen 

 in placing it in this family. 



Stereopneustes. 



De Meijere, 1902. Tijd. Ned. Dierk. Vcreen, (2), 8, p. 9. 

 Type, Stereopneustes relictus de Meijere, 1902. hoc. cit. 



This genus cannot be placed in the Urechinidae because of the struct lire 

 of intcrambulacra 2 and 4, in which the primordial plate is followed by a pair 

 of plates, instead of by one. In this respect it agrees with many nearly allied 



